High and ultra-quality factor (Q) optical resonators have been used in numerous applications, ranging from biodetection and gyroscopes to nonlinear optics. In the majority of the measurements, the fundamental optical mode is used as it is easy to predict its behavior and subsequent response. However, there are numerous other modes which could give improved performance or offer alternative measurement opportunities. For example, by using a mode located farther from the device surface, the optical field becomes less susceptible to changes in the environment. However, selectively exciting a pre-determined, non-fundamental mode or, alternatively, creating a "designer" mode which has one's ideal properties is extremely challenging. One approach which will be presented is based on engineering a gradient refractive index (GRIN) cavity. We use a silica ultra-high-Q toroidal cavity as a starting platform device. On top of this structure, we can controllably deposit, layer or grow different materials of different refractive indices, with nm-scale precision, creating resonators with a GRIN region co-located with the optical field. Slight adjustments in the thicknesses or indices of the films result in large changes in the mode which is most easily excited. Even in this architected structure, we have maintained Q>1 million. Using this approach, we have demonstrated the ability to tune the properties of the device. For example, we have changed the thermal response and the UV response of a device by over an order of magnitude.
Effective monitoring and diagnosis of manufacturing processes is of critical importance. If critical manufacturing process conditions are continuously monitored, problems can be detected and solved during the processing cycle. However, current technology still evidently lags behind practical needs. Microfabricated thin-film thermocouples and strain gauges are attractive for their small size and fast response. It is challenging to fabricate and embed these sensors into metallic components that are widely used in manufacturing. This paper investigates the fabrication, embedding, and characterization of metal embedded thin-film thermocouples and strain gauges. The materials (dielectric and metallic) constituting a complete microsensor were characterized and optimized. The results obtained from characterization and optimization of materials are presented and discussed. Thin-film thermocouples on stainless steel substrates (before and after embedding) were calibrated to elevated temperatures. The behavior of thin-film strain gauges was also studied. The metal embedded sensors demonstrated good accuracy, sensitivity, and linearity that matched the performance of commercial thermocouples and strain gauges well. The metal embedded microsensors are promising for in situ monitoring in hostile manufacturing environments.
Hybrid polymer-silica microcavities with Q factors over 107 using both polymethymethacrylate and polystyrene coatings are shown. A theoretical model based on FEM simulations was developed to explain the relationship between Q degradation and film thickness.
Alloy718 is the nickel-base super alloy well used as gas turbine components under severe operating conditions because of its high strength at high temperature and excellent creep resistance. In this study, a coupling bolt for the gas turbine component is manufactured by hot heading process instead of whole machining in order to improve the mechanical properties. Die shape for the hot heading has been designed by general design rule of hot forging and also optimal process condition has been investigated by finite element method. The initial billet temperature and the punch speed have been determined by $1150^{\circ}C$ and 600mm/s on the basis of finite element analysis, respectively. The coupling bolt has been manufactured by 200ton screw press and evaluated by experiment in order to investigate the mechanical properties. As a result of experiment, the mechanical properties such as hardness, tensile strength and creep behavior have been superior to those manufactured by machining.
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